Servo motors are generally known in the art. A servo motor is an electromechanical device in which an electrical input determines a mechanical output, for example the rotational velocity and torque of a corresponding motor shaft. A servo motor generally includes a rotor surrounded by a nonmoving stator. Winding, or coils of wire, are positioned on the stator. Electrical currents are provided to the winding, producing a rotating magnetic field. The rotating magnetic field interacts with the rotor, causing the rotor to turn. The electrical current is generally provided by a drive. The drive can control the amount of electrical current transmitted to the motor, correspondingly controlling the rotation of the motor shaft. Such drives may be referred to as variable-speed or variable-frequency drives.
It is desired for some end uses of a servo motor to have a high torque to low inertia ratio. A servo motor having a high torque to low inertia ratio provides a fast rate of acceleration of the motor rotor. However, servo motors as described above have limitations on the torque to inertia ratio, especially in applications requiring a larger sized motor. This is due to the larger, higher weight motor and components necessary to rotate a rotor at higher speeds or revolutions per minute (RPM).
In addition, it is desired for some end uses of a servo motor to operate with a higher power density in a smaller overall motor package. A higher power density provides for an increase in efficiency of the servo motor. However, servo motors as described above have limitations in increasing power density and efficiency. One reason includes an increase in winding resistance from end turn waste, effectively reducing stator slot fill. End turns of traditionally wound motors do not provide power or torque, but instead generate unnecessary heat, leading to a reduction of motor efficiency. End turns of the servo motors described above are also susceptible to heat damage, voltage damage, and insulation breakdown due to the buildup of heat at the end turns. The end turns are generally surrounded by air and don't include an adequate thermal path for heat to escape. This can lead to damage to the winding, including a short which can render the servo motor inoperable.
Accordingly, an improved servo motor assembly having an improved electronic current driving system is provided.